With the videophone of the age of the 3rd Generation (3G) mobile communication technology, both parties can see videos of each other in a call. As shown in FIG. 1, a video call is performed by directly selecting a “video call” button when a number of the other party is called through a 3G mobile terminal. The callee can answer the call as if answering an ordinary phone. At this time, the mobile terminals of the both parties automatically start the cameras, perform camera shooting for a user, and the 3G terminal A encodes the video captured from the camera and audio data captured from a microphone through a video/audio encoder in the interior of the terminal, and then multiplexes the encoded video and audio with data and control streams into a single bit stream through multiplexing protocol H.223 and then de-multiplexes the H.223 data into video and audio code streams through a Video Gateway (VIG) A, and subsequently, carries the video and audio code streams in an IP network to transmit to the opposite end. The VIG is an interworking gateway between a circuit switched domain and a packet switched domain. A VIG B to which an opposite end 3G terminal is connected multiplexes the audio/video code streams carried in the IP network into H.223 data to transmit to a callee, i.e., 3G terminal B, and the 3G terminal B firstly de-multiplexes the H.223 bit streams into audio/video code streams, and then decodes the audio/video code streams into audio/video data through an internal decoder to output to a display and an earphone of the 3G terminal, and both parties can see video images of each other and hear voice of each other only after approximately less than 1 second.
However, for most of consumers, it is not always required to show their own videos to the other party each time in a video call, and sometimes, it may be required to hide their own videos, for example, answering a call when having a bath, going to the washroom or answering a call at other times when it is inconvenient to show their own videos, and so on. At this time, connecting their own videos to the other party will make their own privacy gone. How to effectively prevent such events from occurring and make the user use the 3G video call function without scruple becomes particularly important.